[Killer Bee]

the dual battery harness schematic illustrated does not identify any load connections..

body upfitters installing campers, wreckers, utility bodies, emergency services bodies etc. would do that..

the base chassis has no use for an aux battery, it's installed for external 12vdc loads..

winches, spot lights, emergency lights, camper interior lighting, sound systems, etc.

the separation scheme for the two batteries prevents those external loads from draining cranking battery..

a camper would likely have a home run from the aux b+ back to a distribution block..

the schematic only illustrates that connection as a terminal block..

I don't want to interfere with anything you sell but modern 'smart' isolators work great..

they have status light outputs and a bypass trigger for a switch to connect both batteries for jumping..

they're also voltage sensitive and function proactively regardless of key position..

for a restoration, OEM harness should work well for the loads it was intended for..

If anyone needs any help with isolators, happy to help..

good luck!